Solid state television camera with circuit for cancelling noise due to crystal defects

Abstract

In a solid state television camera for producing output signals corresponding to an object image detected by a solid state image sensor, positions of picture elements having crystal defects and the output signal levels of such defective components are previously stored as the defective picture element data in a memory device. Defect compensating signals corresponding to the actual image pickup operating states are formed on the basis of the defect picture element data read out from the memory device to correct the output signals of such defective picture elements in a manner to provide the image pickup output signals with superior picture quality.

What is claimed is: 
     
       1. A solid state television camera with a noise cancelling circuit comprising: solid state semiconductor image sensor means for providing an output signal corresponding to a sensed image, said image sensor means including picture elements arranged in a raster, said sensor means having crystal defects at a plurality of said picture elements causing noise in said output signal at times corresponding to the sampling of the output of said picture elements,   memory means for storing position data indicating the positions of picture elements having said crystal defects and for storing defect level data indicating the level of a compensating signal for compensating the output signal associated with each of said positions, said defect level data being measured at a higher temperature condition than a normal operating temperature condition,   read out means for reading out said position data and said defect level data from said memory means,   temperature sensing means for sensing the temperature around said solid state semiconductor image sensor means,   compensating signal generating means for receiving said position data and defect level data and for generating compensating signals to coincide with the timing of the output signal corresponding with said plurality of picture elements having crystal defects, the compensating signal having the level which is temperature compensated by the defect level data for the temperature output from said temperature sensing means, and   control means responsive to said compensating signal for cancelling said noises from said output signal of the image sensor means.   
     
     
       2. The solid state television camera according to claim 1; wherein said compensating signal generating means includes a two-series signal processing system for separately processing the times in the output signal corresponding to said picture elements having crystal defects and the amplitudes in output signal for picture elements having crystal defects, said amplitudes being in analog form and being sampled in accordance with the times in the output signal corresponding to the outputs of said picture elements having crystal defects for generating defect compensating signals. 
     
     
       3. The solid state television camera according to claim 1; wherein said memory means has stored therein mode codes indicating the locations of white and black flaw defect picture elements, the levels of the white and black flaw defect components contained in the output signals thereof, and the kinds of flaws in said plurality of picture elements; and   further comprising means for discerning said mode codes of said picture elements based on data read from said memory means, the mode codes corresponding to said compensating signals,   said compensating signal generating means forming said compensating signals as a function of the mode codes of said picture elements having crystal defects, said compensating signals being selectively temperature-compensated by the output of said temperature sensing means.   
     
     
       4. The solid state television camera according to claim 1; in which said image sensor means are adapted for variably setting a charge accumulation time in each picture element, and   said compensating signal generating means is adapted to form said compensating signals in association with preset charge accumulating times on the basis of data read out from said memory means,   said output signals from said solid state image sensor means being compensated for crystal defects in picture elements by said compensating signals, the signal level of which is controlled based on the charge accumulation time in each picture element of said solid state image sensor means.   
     
     
       5. The solid state television camera according to claim 1; in which said solid state image sensor means has a signal charge readout mode which can be switched between a first readout mode for reading out the signal charges of the totality of the picture elements in the course of approximately one field period and a second readout mode for reading out the signal charges of the totality of the picture elements in the course of approximately one frame period,   the output in said first and second readout modes of said plurality of picture elements which have crystal defects being previously stored in said memory means as defective picture element data,   said read out means selectively reading from said memory means said defective picture element data associated with the readout mode of signal charges from said solid state image sensor means.   
     
     
       6. The solid state television camera according to claim 1; wherein the distance between a defect position A n  other than the first defect position A o  counting from a reference point, where n stands for any arbitrary integer, and a defect position A n-1  directly preceding said defect position A n  is encoded and stored in said memory means as the position data of picture elements having crystal defects; and wherein, in case of a large distance between said defect position A n  and an adjacent picture position, a dummy defective picture element is used between said defect positions and corresponding data are stored in said memory means. 
     
     
       7. The solid state television camera according to claim 1; wherein said read out means causes said memory means to operate only for a predetermined period including the time during which data necessary for forming said compensating signals at said compensating signal generating means are read out from said memory means, with some time allowance before and after said time duration, said memory means being controlled to remain inoperative during other periods. 
     
     
       8. The solid state television camera according to claim 1; further comprising comparator means for comparing the signal level of the compensating signal generated from said compensating signal generating means with a reference signal level that changes with the image pickup conditions,   said compensating signals having a signal level larger than the reference signal level being taken out as determined by the output of said comparator means.   
     
     
       9. The solid state television camera according to claim 1; in which said image sensor means includes first, second and third solid state image pickup elements, said first solid state pickup element being displaced by one half picture element pitch in the horizontal direction with respect to said second and third solid state image pickup elements, said memory means storing data relating to the positions of the picture elements in said first, second and third solid state image pickup elements having crystal defects and storing data relating to the levels in the output signals at the times corresponding to the outputs of the picture elements having crystal defects, and   said compensating signal generating means being operative to separately form compensating signals of said first, second and third solid state image sensor elements on the basis of data read out of said memory means, and to separately adjust the locations of generation of said compensating signals,   said compensating signal generating means generating said compensating signals for said solid state image sensor devices at times corresponding to the sampling of the output of said crystal elements having crystal defects in said first, second and third solid state image sensor devices and adding the compensating signals to the output signals of said first, second and third solid state image sensor devices for compensating the crystal defects.